JPS6155388A - Vane pump - Google Patents

Abstract

PURPOSE:To reduce the load torque of a pump easily by incorporating such an arrangement, that the discharge port can be put in communication with its mating suction port by means of a selector valve, into at least one of the working chambers of a vane pump having a plurality of working chambers. CONSTITUTION:Cam ring of a vane pump is equipped with three large dia. parts 1-3C so as to form three working chambers. A discharge port OP and a suction port IP are provided at each large dia. part in front and behind it. Two of these three working chambers are equipped, between their discharge ports DP2, OP3 and the discharge convergent line 50, with a selector valve V1, V2 which can be connectible to the suction ports IP2, IP3, respectively. Accordingly, two working chambers can be unloaded selectively by changing over the selector valves V1, V2 appropriately, which will ensure reduction of the load torque of the pump.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a vane pump that supplies pressurized fluid to a power steering device or the like.

<Prior Art> In conventional pumps for power steering devices, when the pump rotation speed exceeds a predetermined number, a flow rate control valve controls the discharge flow rate to be constant.

<Problems to be Solved by the Invention> The flow control valve used in the above-mentioned pump has a structure in which the spool is slid by a pressure difference generated before and after the throttle, and a part of the discharged fluid is bypassed to the bypass passage. Therefore, when the pump rotates at high speeds, the bypass flow rate only increases, and the discharge flow rate from the pump itself cannot be reduced. Therefore, the load torque increases and energy loss increases. Ta.

Means for Solving the Problems> The present invention has been made in order to solve the problems of the conventional art.
It is composed of three cam curves formed with a phase difference of degrees, and three sets of suction ports and discharge ports are arranged corresponding to these three cam curves. The configuration is characterized in that at least one discharge boat is connected to a switching valve that selectively communicates the discharge boat with the delivery side or the suction port side.

<Operation> Since the present invention has the above configuration, when the pump rotates at low speed, the discharge fluids from the three discharge boats are combined to ensure the required flow rate. Furthermore, when the pump rotates at high speed, the switching valve is switched to communicate at least one of the three discharge boats with the suction port.

As a result, a portion of the discharge fluid is introduced into the suction port, and the bypass flow rate from the flow control valve is reduced accordingly, and as a result, the load torque of the pump can be reduced.

<Example> Embodiments of the present invention will be described below based on the drawings.

In FIGS. 1, 2, and 3, 10 indicates a pump housing, and a bottomed hollow chamber 11 is formed in this pump housing 10, and this hollow chamber 11 opens at one end of the pump housing 10. There is. pump housing 10
An end cover 12 that closes the opening is fitted to one end of the cover 12, and is further prevented from coming off with a circlip. Inside the hollow chamber 11 surrounded by the pump housing 10 and the end cover 12, there is a cam ring 14, a side plate 15 that is in contact with one side of the cam ring 14, and a side plate 15 that has one end that is in contact with the other end of the cam ring 14 and a back side that is in contact with the other end of the cam ring 14. A side plate 16 facing the end cover 12 is housed, and one side plate 15 is fitted into a bearing hole 10a of the pump housing 10. The cam ring 14 and the pair of side plates 15 and 16 are aligned in phase by a positioning pin 18 supported between the pump housing 10 and the end cover 12.

A cam surface C consisting of three cam curves CI, C2, and C3 having a phase difference of 120 degrees in the circumferential direction is formed on the inner periphery of the cam ring 14, and 11 vanes 21 that slide on this cam surface C are radiated. A rotor 22 that is slidably inserted in the cam ring 1-4 is housed in the cam ring 1-4. Such a rotor 22
The dimensions in the axial direction of the vane 21 are somewhat smaller than those in the axial direction of the cam ring 14, and the pair of side plates 15, 16 are arranged on both sides of the cam ring 14 (I[1
Appropriate side clearance (
axial clearance) is maintained. Rotor 22
is splined to one end of a rotating shaft 24 rotatably supported by a bearing 23 fitted into a bearing hole 10a of the pump housing 10.

A plurality of pump chambers partitioned by vanes 21 are formed between the cam surface C of the cam ring 14 and the outer peripheral surface of the rotor 22, and the volume of each pump chamber changes as the rotor 22 rotates. On each side of the pair of side plates 15, 16 that are in contact with the rotor 22, there are three suction ports (IPI, IF5.) corresponding to the pump chambers that perform the expansion process. IF5 also has three discharge boats OPI, OP2. OP3 is formed respectively.

The discharge boats OPI, OP2. The fluid discharged from OP3 is controlled by a flow control valve 40 shown in FIG. The flow rate control valve 40 has a spool 42 that is slidably fitted into the valve hole 41, and the spool 42 divides the inside of the valve hole 41 into two fluid chambers 41a and 41b. A discharge passage 5 is provided in this - side fluid chamber 41a.
The fluid discharged from the fluid chamber 4 is introduced into the other fluid chamber 4.
The fluid that has passed through a restriction 44 formed in a union 43 is introduced into 1b. Therefore, the spool 42 compresses the spring 45 due to the pressure difference before and after the throttle 44 and slides to control the opening degree of the bypass passage 46, and as a result, a portion of the fluid discharged from the discharge passage 50 is directed to the bypass passage 46. It is bypassed so that a constant flow rate of fluid is always delivered from the delivery port 47.

In the pump having such a configuration, the present invention provides the discharge boats OPI, OP2. The following circuit is provided to control the fluid flowing out from OP3 to the discharge passage 50.

That is, the discharge ports ○Pi, OP2. Discharge passages 51, 52.53 are connected to OP3, respectively.
After being merged with the flow rate control valve 40, it is communicated with the flow rate control valve 40.

Among these three discharge passages 51, 52, 53, the discharge passage 5
2. In the middle of 53, there is a solenoid switching valve V2. V3 is inserted.

This electromagnetic switching valve V2. V3 is sequentially switched as the pump rotation speed increases, and the discharge passage 52.53 is communicated with the suction port 1-IF5, IF5 via the return passage 55.56.

In addition, the above-mentioned inhalation port) IPI, IF5. The IF 5 communicates with a suction passage 61 communicating with a reservoir (not shown) and a bypass passage 46 communicating with the flow rate control valve 40 via an annular groove 60 formed in the hollow chamber 11 . The discharge port OPI also communicates with a pressure chamber 63 formed between the end plate 12 and the side plate 16.

Next, the operation of the vane pump having the above configuration will be explained.

First, when the rotating shaft 24 is driven by the engine, the rotor 22 rotates, and the working fluid is supplied to the pump chamber that performs the expansion process from the suction passage 61 to the three suction ports I.
P,,1. IP2. Three discharge ports O
Pressure fluid is discharged through PI, OP2, and ○P3.

When the engine is rotating at low speed, the solenoid switching valve V2.
V3 are all in the position ■, therefore, as shown in FIG. 2, the three discharge ports OPI, OP2 . ○The pressure fluids discharged from P3 are combined and discharged into the discharge passage 50. Engine speed is low (three discharge ports OP 1
．． ○P2. When the discharge flow rate from OP3 is small, the flow rate control valve 40 is not operated and the entire amount of the discharge fluid is sent out from the outlet port 47.

Thereafter, when the engine speed gradually increases to the speed N1 shown in FIG. 4, the three discharge ports OPI
, OP2. The discharge flow rate from OP3 exceeds the required flow rate Q1 as shown in FIG. 4A.

Therefore, from this point on, the flow rate control valve 40 is activated to bypass the flow rate greater than or equal to the required flow rate 01 to the bypass passage 46.

Further, when the engine speed increases to N2, the electromagnetic switching valve V2 is switched to the position (■), and the discharge fluid from the discharge port OP2 is returned to the suction port IP2. Therefore, as shown in FIG. 4, only the fluids discharged from the discharge ports OPI and OP2 are discharged into the discharge passage 50, and the pump load is reduced accordingly.

Thereafter, as the engine speed increases, the discharge flow rates from the discharge ports OPI and OP2 gradually increase, but fluid with a required flow rate of 01 or more is bypassed to the bypass passage 46 by the flow rate control valve 40.

At this time, the discharge port has already been switched between two states and is controlled so that the discharge flow rate from the discharge port itself is reduced, so the bypass flow rate accompanying the operation of the flow control valve 40 is also small, and the pump load is accordingly reduced. Become.

Furthermore, when the engine speed reaches N3, the solenoid switching valve V2
．． Both V3 are switched to the ■ position, and the discharge port OP2
．． The discharge fluid from OP3 is sent to suction port IP2. Returned to IP3. Therefore, as shown in FIG. 4C, only the fluid discharged from the discharge port ○P1 is discharged into the discharge passage 50, and the pump load can be further reduced.

After that, as the engine speed increases, the discharge port ○P1
The discharge flow rate increases, but as before, fluid with a required flow rate of 01 or more is bypassed by the flow rate control valve 40. Also at this time, the discharge port OP2. The discharge flow rates from O and P3 have already been stopped, so the amount of bypass is also small, and the pump load is further reduced.

Note that the degree of reduction in load torque due to the vane pump is calculated as follows.

First, the solenoid switching valve V2. Consider the case where V3 is not switched.

The theoretical discharge flow rate per revolution from one discharge port of an 11-vane pump is vth, the rotation speed is N, and the pressure on the load side is P (however, the pump internal pressure PXN is
(Since there is a differential pressure ΔP at 4, it is PIN−ΔP+P.) If torque loss due to friction inside the pump is ignored, the theoretical load torque Tthl becomes the following equation.

Here, PL, P2. P3 are respective discharge ports OP1.
OP2. The pressure at OP3 is P1=P2=P3=P
Since xN=ΔP+P, on the other hand, when calculating the theoretical load torque when switching the solenoid switching valve ■2, P2=O, P1=P3=Δp+p, = −
T th 1 . This is 2/3 of the load torque compared to the case where the electromagnetic switching valve V2 is not switched.

Furthermore, when both electromagnetic switching valves v2 and V3 are switched, from P2=P3=O, P1=Δp+p, = −−T t
h, and by switching and controlling the electromagnetic switching valves ■2 and ■3 as described above, the load torque can be reduced and an energy-saving pump can be achieved.

In the above embodiment, the case of constant flow rate control was explained, but when the engine reaches a predetermined rotation, the flow rate is lowered.
The same can be applied to the case of so-called drooping control.

<Effects of the Invention> As detailed above, the vane pump of the present invention has three sets of suction ports and discharge ports corresponding to the three cam curves for sucking or discharging working fluid into the pump chamber. , a discharge passage is connected to each of the three discharge ports, and a switching valve is inserted in at least one of the three discharge passages to selectively connect the discharge passage to the delivery side or the suction boat side. Therefore, the flow rate discharged from the pump itself can be reduced, and as a result, the bypass flow rate from the flow rate control valve can be reduced, which has the advantage of reducing the load torque of the pump.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention; FIG. 1 is a cross-sectional view of the vane pump of the present invention, FIG. 2 is a cross-sectional view taken along line nn in FIG. 1, and FIG. II [line cross-sectional view,
FIG. 4 is a diagram showing the relationship between engine speed and pump discharge flow layer. 10...Pump housing, 14...Cam ring,
21.22...Rotor, IPl, IF5, IF5・-
・Suction port, OPl, OF2゜OF2...Discharge port, 51.52.53...Discharge passage, V2. V3...
・Solenoid switching valve.

Claims (1)

[Claims] A pump housing, a cam ring fitted into the pump housing and having a cam surface made of three cam curves having a phase difference of 120 degrees on its inner circumference, and a rotor housed in the cam ring and connected to a rotating shaft. and the cam ring, the vanes are housed in the rotor at equal intervals on the circumference to form a plurality of partitioned pump chambers, and the vanes are arranged to draw in or discharge working fluid into the pump chamber. In a vane pump having three sets of suction ports and discharge ports corresponding to three cam curves, a discharge passage is connected to each of the three discharge ports, and the discharge passage is sent to at least one of the three discharge passages. A vane pump characterized by inserting a switching valve selectively connected to the side or the suction port side.